Growth, repair or maintenance of mature tissues often requires recruitment of new cells from stem cell precursors. In zebrafish, melanocytes are re-established from stem cells when ablated in the embryo, or in regenerating fins following amputation. Our goal is to understand the cellular andmolecular basis of mechanisms that establish stem cells in the embryo, or how stem cells survey their environment, and then are recruited to replace missing cells in regenerating tissues. Accordingly, we will study the role of a growth factor receptor, kit, or other candidate genes and mutations, in recruiting melanocyte stem cells in larvae and in regenerating fins, or how different signal transduction pathways affect different cellular functions of melanocyte migration or survival. Specifically, we will:(1) identify kit-dependent signal transduction pathways specific to melanocyte migration or survival, by targeted morpholino-inactivation or dominant enhancers of a sensitized kit mutation.(2) Determine the role of kit in establishing or recruiting melanocyte stem cells that make new melanocytes following larval melanocyte laser ablations, and identify mutations that prevent melanocyte recovery.(3) Order kit (a presumptive stem cell marker) and trp2 (a presumptive melanoblast marker) expression with respect to the first cell division in regeneration melanoblast lineage.(4) Assess whether pyewacket mutation affects the allocation between stem cell and melanoblast fates following the first regeneration cell division.This work will have a general impact on understanding how growth factor receptors signal through multiple pathways to affect multiple cellular functions and how latent stem cells are recruited to fill cellular deficits. This work will also have specific impact on understanding the basic biology of melanocyte development that will provide insight into the growth control mechanisms gone awry in human pigmentation disorders, melanoma or other cancers.